TY - JOUR
T1 - Ac impedance techniques to study oxidation process of tunnel barriers in CoFe- AlO x -CoFe magnetic tunnel junctions
AU - Huang, J. C.A.
AU - Hsu, C. Y.
N1 - Funding Information:
This work has been supported by the National Science Council of the ROC under Grant No. NSC 94-2112-M-006-003, Micro-Nano Technology Research Center of National Cheng Kung University under Grant No. H93-A930, and Taiwan spin research center of National Chun Cheng University under Grant No. 93-EC-17-A-01-S1-026. The authors would like to thank Professor S. Y. Chu and P. C. Kao for kindly assistance in using the impedance analyzer. FIG. 1. The experimental (symbols) and the fitting (solid curves) complex impedance spectra for the CoFe – AlO x – CoFe MTJs with t ox = (a) 30, (b) 50, and (c) 80 s. FIG. 2. The experimental (symbols) and the fitting (solid curves) complex impedance spectra for the CoFe – AlO x – CoFe MTJs with t ox = (a) 100, (b) 120, and (c) 130 s. FIG. 3. (a) The dc four-point probe resistance, interfacial resistance obtained from complex impedance (CI) and complex capacitance (CC) spectra with t ox = 30 – 130 s . (b) The interfacial capacitance obtained from the analysis of CI with t ox = 30 – 130 s . The inset of Fig. 3(b) shows the top ( C ti ) and bottom ( C bi ) interfacial capacitances for the CoFe – AlO x – CoFe MTJs. FIG. 4. The relaxation frequency of the AlO x and CoFeO x layers of MTJs analyzed by the CI and CC techniques (symbols). The solid curves are the average values of the relaxation frequency obtained from the CI and CC spectra.
PY - 2005/9/15
Y1 - 2005/9/15
N2 - The complex impedance spectra of CoFe- AlOx -CoFe tunnel junctions with under-, proper-, and overoxidized tunnel barriers have been investigated by ac impedance techniques. Two sets of parallel resistance (R) and capacitance (C) elements and a R element in series, modeling the impedance contributions of the metal-oxide interfaces and bulk insulating layers, are employed to describe the impedance spectra of under- and proper-oxidized junctions. This model, however, reveals a discrepancy for overoxidized junctions. This discrepancy can be reconciled by including a third set of parallel RC element, which suggests the appearance of overoxidized CoFeOx layer upon the bottom electrode. From further analysis of interfacial capacitance as a function of oxidation time, the bottom interfacial capacitance widely diverges from the top interfacial capacitance and can be related to the oxidation process of tunnel barrier. The analyzing results of impedance technique are also consistent with the results by complex capacitance technique.
AB - The complex impedance spectra of CoFe- AlOx -CoFe tunnel junctions with under-, proper-, and overoxidized tunnel barriers have been investigated by ac impedance techniques. Two sets of parallel resistance (R) and capacitance (C) elements and a R element in series, modeling the impedance contributions of the metal-oxide interfaces and bulk insulating layers, are employed to describe the impedance spectra of under- and proper-oxidized junctions. This model, however, reveals a discrepancy for overoxidized junctions. This discrepancy can be reconciled by including a third set of parallel RC element, which suggests the appearance of overoxidized CoFeOx layer upon the bottom electrode. From further analysis of interfacial capacitance as a function of oxidation time, the bottom interfacial capacitance widely diverges from the top interfacial capacitance and can be related to the oxidation process of tunnel barrier. The analyzing results of impedance technique are also consistent with the results by complex capacitance technique.
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U2 - 10.1063/1.2058177
DO - 10.1063/1.2058177
M3 - Article
AN - SCOPUS:26244454735
VL - 98
JO - Journal of Applied Physics
JF - Journal of Applied Physics
SN - 0021-8979
IS - 6
M1 - 064901
ER -